1. Field of the Invention
This invention pertains to machines for freezing and dispensing a confectionery product, particularly soft ice cream, the machine consisting in part of a freezing chamber, a liquid product reservoir located above the freezing chamber, and a tubular communicating line between the liquid product reservoir and the freezing chamber. The invention is particularly addressed to an improved air-mix feeding element for controlling the flow of air and liquid product through the tubular communicating line to assure the proper overrun in the resultant product. Of particular importance is a checkvalve included within the air-mix feeding element which is easily serviced and is the form of a pair of opposed liplike portions adapted to sealingly engage an interstitial flat plate.
2. Description of the Prior Art
Machines for freezing and dispensing a soft confectionery product such as frozen custard or ice cream generally include a freezing cylinder housing a rotary dasher. Positioned above the freezing chamber is a reservoir containing a suitable mix in the form of a liquid product which when subsequently frozen under the proper conditions will yield the desired flavor and texture. The dasher in the freezing chamber acts to whip air into the mix as well as circulate the product within the freezing chamber to assure reasonably uniform temperature, texture, and the like.
The freezing chamber and liquid product reservoir are connected in some manner so as to permit a suitable amount of new liquid product to move from the reservoir to the freezing chamber at the same time as some frozen product is being dispensed from the freezing cylinder. In the machines to which this invention applies the freezing chamber and liquid product reservoir are typically connected by an open tubular communicating line extending between the two. An air-mix feeding element may be positioned near the liquid product reservoir end of this tubular communicating line to control the amount of mix and air which is drawn into the freezing chamber. An example of the prior art is illustrated in FIG. 2 of this application. A common failing of machines of this type has been the inability of the machine to sustain the proper overrun in the dispensed product for any extended period of time.
When the frozen product is not being dispensed from the freezing cylinder the machine must periodically cycle on and off so as to maintain the temperature of the frozen product in the freezing chamber at the correct temperature. When the machine cycles on the beater or dasher also runs in order to keep the frozen product soft so it can be dispensed when needed. As the machine remains in this "standby" conditon for any extended period of time, air will tend to separate from the frozen product and escape via the tubular communicating line between the liquid product reservoir and the freezing chamber. The resultant frozen product when finally dispensed will not contain as much air as it should and as a result will lack proper taste, not stand up in a cone, and often becomes grainy. Soft ice cream normally dispensed from an apparatus of this type is most desirably served at 19.degree. Fahrenheit with a 4-5% butterfat mix content and an overrun of approximately 50%. Typically, however, a gravity fed machine of this type not utilizing the advancement of this invention will average only about 25- 30% overrun.
Other solutions have been suggested to this problem of maintaining the overrun in the frozen product including the use of elaborate pumps for introducing pressurized or compressed air into the freezing chamber. Examples of machines using an external air pressurizing device are to be found in U.S. Pat. Nos. 3,330,127, 3,196,633, 3,147,601 and 2,565,121. The disadvantage of the addition of such elaborate pumping schemes is the increased energy which is required to run the apparatus as well as the non-convertability of most older type gravity fed machines. The advancement provided by this invention on the other hand is fully adaptable to a large group of machines of this type and has been designed to permit very simple modification and replacement even by those having only a modicum of skill in this art.